Field of the Invention
The present invention relates to a hot-melt adhesive comprising a random copolymer of an .alpha.-olefin having 4 to 12 carbon atoms with an aromatic vinyl monomer. More particularly, the present invention relates to a hot-melt adhesive comprising a copolymer of an .alpha.-olefin having 4 to 12 carbon atoms with an aromatic vinyl monomer, which is excellent in adhesiveness, workability and environmental aging resistances such as thermal aging resistance, and can be used in various fields such as packaging, bookmaking, pouchmaking, woodworking, can manufacturing, construction and sanitary use.
The present invention also relates to a composition comprising the above-mentioned copolymer and a tackifier, which can be used as a hot-melt adhesive or a heat sealant.
Recently, the hot-melt adhesive has been increasingly used in various fields since it is superior to prior art solvent type adhesive in coating properties, safety, cleanness for working atmosphere and energy savings. Compositions including a base polymer such as natural rubber, ethylene-vinyl acetate copolymer, a styrene-butadiene-styrene block copolymer have been used as prior art hot-melt adhesives and heat-sealing adders.
However, since the compositions including a base polymer such as natural rubber, a styrene-butadiene-styrene block copolymer, a styrene-isoprene-styrene copolymer have a lot of double bonds, they are poor in thermal resistance stability and have problems that oxidation, decomposition and coloring do not only occurs on application, but also the bonding performance changes with time after bonding. An ethylene-vinyl acetate copolymer based composition has a poor adhesiveness to polyolefin resins such as polyethylene and polypropylene.
For the prior art hot-melt adhesive, it is generally necessary to compound a tackifier into a base polymer. A single-component resin for adhesive having both performances of the base polymer and the tackifier has been demanded for simplicity of steps and preventing variations of products on compounding.